Conventional portable transceivers, such as portable one-way radios, are controlled with a mechanical push-to-talk switch which must be depressed manually each time the operator wants to transmit. In many instances the manual operation is inconvenient. As a simple example, repairmen receiving instructions by radio may need both hands to do the repairs. Many other instances where handfree operation would be convenient, or even necessary, will be apparent to operators as well as those skilled in the art.
Some speaker phones for telephones and the like contain circuits that are voice operated. However, these circuits are relatively complex and require large amounts of voltage and power. Clearly, such circuits could not be used in portable transceivers where the amount of voltage, power usage and size are crucial.